The Vow of Mist and Sky
by Amalialia
Summary: Mukuro never lied about his true goal, and Tsuna never truly doubted his Mist Guardian's intentions. What happens when Mukuro finally comes to claim him? One-shot.


_Note: the idea for this short fic came from watching the end of the anime and feeling a bit lost without more Reborn episodes to watch! Tsuna really grew up over the course of the series, and so I wondered what would happen if Mukuro ever fulfilled his promise from way back in the Kokuyo Land arc. I haven't read the manga (yet!) so I apologise if I get anything wrong, but hopefully both Mukuro and Tsuna are mostly in character. Please let me know if you have any thoughts or corrections, I'd love to hear from you!_

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When the promised day finally came, Tsuna was calm.

_My target is and will always be you._

It was long after their battle in the future with Byakuran, long after he'd graduated from Namimori and moved to Italy. Months after he'd finally accepted the position as 10th generation boss of the Vongola family and been officially initiated. He'd been so idealistic as a child, always denying what he felt now had been inevitable from the moment he and Reborn ever crossed paths. He could never escape it, nor could he escape what was to come.

_I will destroy the Mafia._

There was a knock at his door that day. Echoes of his own resolve floated in his mind. The day he promised to destroy the Vongola if their bloody and sinful past was the fate of those who wielded their power. But he knew this wasn't the case. He knew because the First had been different. Tsuna was different. And his family was different.

"10th, may I come in?" It was unmistakably Gokudera's voice. But his inherited intuition had come a long way since he was a teenager. He knew who it was.

"Come in," he said politely.

The door swung open, and three people stood there. Gokudera, Fuuta and Chrome. Two of his guardians, and the now much taller kid brother he'd always looked out for. But it wasn't really them. He didn't need to see their right eyes to know who was controlling them. He'd never forgotten that his friends had been compromised back in Kokuyo Land, back when he was just an inexperienced and naive kid.

"Hello Mukuro," he said pleasantly. Gokudera cocked his head uncharacteristically.

"Oya," he said with interest. "Your super intuition is even better than I expected."

All three of them entered, and closed the door behind them. He didn't flinch when Fuuta locked the door. He was already inside an illusion. Nobody from outside the room would interfere.

Chrome looked confused, holding Mukuro's trident tentatively, and he realised that Mukuro only had a tenuous control over her. She'd grown so much more powerful since they'd first met. Tsuna suspected that her illusionary power rivalled even Mukuro's now, despite his superior age and experience. It made him a bit sad, somehow. He'd never wanted to drag all these innocent people into such a life.

"You know why I'm here then," Fuuta said, glancing at Chrome.

"Yes," Tsuna said. Just as Daemon had betrayed Giotto, so too would Mukuro betray him. And just as the Vongola Primo had seen it coming, so too had the Vongola Decimo. Like a faintly glowing beacon for days, months, years.

"You're not going to run?" Gokudera said, his eyes focused on Tsuna. Tsuna's heart panged when he caught a glimpse of tortured pain flicker across Gokudera's face. He was trying so hard to fight it. To fight Mukuro's control over him.

"No. I've accepted this, and Gokudera-kun should too," Tsuna said softly, looking at his right-hand man. Gokudera chuckled.

"He never will," he said. "The smoking bomb will chase me till the day he dies." Which reminded Tsuna.

"I have conditions," he began firmly.

"Is that right? And why should I follow your conditions?" Chrome asked, switching the trident slowly from hand to hand.

"Because I've informed Hibari of this decision," Tsuna replied evenly. "If any of my conditions are not followed, I've given him permission to assassinate me. And I've also officially named Xanxus as my successor in case this should happen. Since it is my dying will, the rings will allow his inheritance."

Gokudera's lip curled a bit, and his eyes narrowed. Tsuna had deliberately chosen the fiercely proud leader of the Varia because he knew Mukuro would not be able to easily compromise Xanxus. And Mukuro knew that as well.

"I'm listening."

"You are not to harm any of my family. That includes both Guardians and the extended family as well as anyone allied with the Vongola. You are not to tell them that you are controlling me, I don't want unnecessary worry. Which means that, as much as possible, you must convince them that nothing has changed. Further, while I permit your destruction of the mafia, I forbid you to use violence unless absolutely necessary. I understand that some situations may result in the need for persuasion, but you are not to kill or harm anyone if there are alternative routes."

"Soft as ever, Vongola Decimo." Fuuta crossed his arms.

"Finally, once you achieve your goal, you will reform the Vongola family as per its original goals; that is, to protect the people. We shall no longer be associated with the mafia, but instead exist as a vigilante organisation that is available to assist those in need. You will release all current inhabitants of Vindice prison, including yourself. And when this is done, you will relinquish your control over everyone."

"Including you?"

"Yes." He hoped that this much would be enough for his guardians to continue onwards without him, if there was the promise of it all being over one day. Maybe Gokudera would accept this, if nothing else. His ever loyal companion, who'd always stuck by him no matter what stupid choice he made. Would he ever understand and forgive Tsuna for this betrayal?

Gokudera paused, considering Tsuna's words.

"Fine."

"Promise?"

"What are you, ten years old?" Chrome shook her head. "Yes. I promise."

Tsuna breathed out, a huge weight released off his shoulders. He could sense that Mukuro was sincere, and this relieved him greatly.

"If you saw this coming, why didn't you stop me?" Gokudera asked. "Your guardians would have been more than willing to protect you. They might have even succeeded."

Tsuna smiled a little, distantly.

"I've known for a long time that it would be you, Mukuro. We live in a world that was never meant to be what the Vongola stood for. I want to stop the mafia; I don't want any more innocent people to get hurt. But you're right, you know, I'm too soft to be the one to fix this mess that they've made. You understand that best of all. If anyone can destroy the mafia, and restore the Vongola family to what it was always meant to be, it's you. Even Primo understood this. You're different to Daemon, because you witnessed firsthand the cruelty of the mafia and you want to make sure that never happens to anyone ever again. I respect that resolve, and so I trust you. "

"Primo? He was a fool to trust Daemon Spade. It cost him dearly. Why are you making the same mistake?" Fuuta said resentfully.

"It wasn't a mistake. It was a necessary sacrifice. The First understood that there was a future that required him to step down, and so he did. What followed wasn't quite what he had hoped, but that is why we learn from the past. And the future," he added wryly, as an afterthought. He paused, remembering all that they had fought for. And all that they had lost in the process.

"Any other conditions?" Chrome prompted, breaking into his thoughts. Tsuna felt Gokudera and Fuuta approach him from either side.

"I already told you, I'm not going to run," Tsuna said.

"Safety precaution," Gokudera whispered in his ear. "Can't have last minute changes of heart."

Gokudera and Fuuta gripped him arms gently and lifted him to his feet. Tsuna allowed it, since it wasn't really worth protesting over. He glanced out the window, at the infinite sky. At the grouping clouds, at the stormy cumulo nimbus and flashing lightning far away on the horizon. At the setting rays of the sun and the shimmering reflection off the waters of the lake. He hoped that they would come to understand, as he knew they would figure out what had happened.

Chrome approached the desk, the trident brandished in front of her. Her hands were shaking, and Tsuna knew that she was conflicted this time about obeying her beloved Mukuro-sama.

"It's okay, Chrome," he said with a smile. "It'll be okay."

He stood tall and told himself that this was the right thing to do. He _knew_ it was. Deep within his heart, he felt the faint pulse of Primo's presence reassuring him, and he was comforted. Even though it would take years… even though Kyoko would move on without him… it was necessary.

For the sake of the Family. _This is our vow._

He didn't jump when Chrome nicked an almost unexposed part of his neck, beneath his collar, and he didn't panic when he felt Mukuro's essence invading his senses, as his brain became foggy and unfocused. Gokudera and Fuuta slumped to the floor next to him, evidently worn out from being controlled against their will for that long. Tsuna knew they were okay, Mukuro had kept his promise. It was probably better if the real Gokudera wasn't awake just yet in any case.

"Boss…" Chrome's eyes were welled up with tears, and the trident clattered to the ground. Tsuna could feel that he still had a little bit of control left, and he lifted his hand to her cheek, catching the tears as they rolled down. What he couldn't see was that his right eye was slowly clouding over, was slowly fading from its normal warm brown into a harsh red. Chrome backed away, her violet eyes still bright with tears.

"There should have been another way," she whispered, and Tsuna felt Mukuro hesitate. Chrome never disagreed with his will. But she'd come so far from the nervous, apologetic girl Mukuro had saved years ago, and was attached to the Vongola boss, having seen his resolve and kindness many times over, on the battlefield and everywhere else. She fled from the room, easily breaking through the illusion.

Tsuna was left alone as he lost control, feeling his essence fade away, growing more and more tired. Like he needed a long sleep in a faraway place. He felt Mukuro's emotions surge through him: bitter triumph tinged with strains of guilt and regret, and uncertainty. He shook his head, still able to do this much.

"Mukuro," he whispered. _I forgive you._

A single tear escaped the corner of his right eye, against his will. Was it his? Or Mukuro's…

_You always hated to fight, didn't you, Sawada Tsunayoshi? Even though you were thrown into battle after battle. _

The Sky ring on his slender finger glinted in the fast fading light of sunset. Over time, Tsuna had come to view its weight there as both a burden and a blessing, as a symbolic reminder of always accepting the good with the bad. In the glass dome of the ring, the sky and all its components were reflected, inverted.

_The rest is up to you, ne, Mukuro-kun?_

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_Please review and let me know what you thought! :)_


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